Loud-speaker



F. SALDANA LOUD SPEAKER May 14, 1929.

Filed Dec. 1926 2 Sheets-Sheet May 14, 1929.

F.SALDANA LOUD SPEAKER Filed Dec. 8, 1926 2 Sheets-Sheet 2 W 021% A MM Patented May 14, 1929.

FELIPE SALDANA, OF PARIS, FRANCE.

LOUD-SPEAKER.

Application filed December 8, 1926, Serial No. 158,389, and in France December 17, 1925.

The object of this invention is a loud speaker for wireless telephony, and the invention is specially concerned with the construetion of the vibrating parts and of the resonant diaphragm, its purpose being to suppressthe nasal effect, obviate distortion, and generally to perfect the sound reproduction. I The invention relates to loud speakers 0 the acoustic diaphragm type, that is to say instruments which have no cover, but have their armature fastened to a reed secured in the casing of the instrument and to a diaphragm which suitably amplifies, the sound. It is a defect of existing instruments of this 1 kind that the reed and the diaphragm have well marked natural frequencies of vibration dependent on their sha e and dimensions, and these natural vibrations are superposed on theforced vibrations imposed by the electromagnet on its armature, with the result that listeners hear sounds which are resultant of all the vibrations, and which are a distortion'of the sound intended to be repro duced. The present invention eliminates this defect by preventin or reducing to a minimum the natural vi rations of the reed and diaphragm.-

Inessence the invention consists in subdividing the vibrating reed into several branches 0 having different natural frequencies, so that the vlbrations of the reed as a whole are neut alized.

A further feature of the invention is the adoption of two diaphragms in lieu of one; they maybe of conical form with their apices towards one another,and must have different natural frequencies.

Other features of the invention will a pear from the detailed description hereinafter.

The drawin 5 show by way of example a construction 0% loud speaker embodyingthe invention;

Figures 1 and 2 are axial sections on planes at right an les of the electromagnet, vibratin reed, mil armature;

igure 3' is a perspective view of one constriliction of asynchronous reed' upona larger sca e;

diap agm above referred to;

Figures 5 and 6 are a transverse section and perspective view respectively illustrating a mountln of the instrument which makes for ampli cation of the sound.

In the construction illustrated the vibrating reed is made up of three branches. The

- This balancin alsohelps the re Figure 4 shows the construction of double centre part 1 is the armature of the electromagnet 2 From it proceed three branches 3, 4 and 5. It may be seen from Fi ure 3 that the branch 3 is thinner than the branches 4 and 5, and that the branch 4 is of less width than the branch 5. Consequently the natural frequencies 'of the three branches are all different, and the com osite reed is asynchronous, that is to say it as no natural frequency of vibration, or at least its natural vibrations are instantly damped out.

. It is obvious the branches may be different-- 1y arranged, or may be more in number. For instance the armature 1 might be the centre of the four arms of a cross. Moreover by dividing a plate b radial slits, and making its several parts 0 different thickness any desired number of branches may be formed each secured to the casing at the end remote from the armature. The invention is not limited to a particular number or particular arrangement of branches resulting in an asynchronous reed.

"Figure 4 shows the construction of the asynchronous diaphra m. The stem 6 of the reed armature is attac ed to two diaphragms 7, 8, which are approximately of con1cal form with their agices in op ition. The cones are truncate and clos by plates 10 which are fastened to the stem 6 by nuts 9. The dia hra-gms are tensioned in frames 11, 12 of suitable form, and are designed to have different natural frequencies of vibration. This arrangement besides being asynchronous, enables greater tension to be ut on the diaphragms without increasing t e pull on the armature, since the pull exerted by the one diaphragm is opposed by that of the other. roduction, and the fact t at there are two iaphragms means that there is double the vibrating surface'for a given space occupied.

The material of which the diaphragms are made has a considerable effect upon the re reduction. Paper, card, and varnished fa rics do not give altogether satisfactory results.

I have found that better results are obtained fromcelluloid or similar products based on acetate and nitrate of cellulose. Very good results may be obtained from pa er or fabric coated with celluloid. The

eel uloid is moulded hot into a form such as is shown in Figure 4. This shape is ap roximatively that which is obtained by ta ing a thin sheet of a plastic and elastic material such as rubber of about 0.08 to 0.15 m/m., fixing it on the periphery of a washer such as 10 and stretching it by fixing it on the periphery of a frame 11 so that the diaphragm will have substantially an hyperboloidous shape. The shape of the frame 11 is preferably square, or oval. I have found that a circular shape would be less efficient and reliable. It is preferable that the thickness of the diaphargm should diminish progressively from the periphery towards the centre, and this only possible with celluloid or other plastic material, not with paper or fabric.

I have also found it preferable that each of the two diaphragms should be composed of more than one material; for instance they may have a zone of thin wood next the periphery extended to the centre by a thin sheet of celluloid.

The diaphragms may be made more sonorous by embodying in the celluloid by any suitable process finely divided metal such as a metal powder, on the whole surface or only on a part of that surface.

I have found that the construction of the diaphragms or of a diaphragm with variations in the thickness, with various materials, or with certain parts only metallized are very suitable in order to obtain aperiodic diaphragms.

It will be obvious that these features, namely the materials described, the varying thick ness of diaphragm, and the zones of different composition, may be adopted in existing instruments having but a single diaphragm, and

such applications are to be considered within the ambit of this invention.

The reproduction of sound by the instrument may be still further improved and amplified by mounting it in the manner shown in Figures 5 and 6.

As may be seen from these figures the complete instrument comprises a frame of wood 13, Within which is fixed by dowels or other suitable means a sounding board 14. The casing 15 of the telephone receiver is secured in the board 14. This board may be of any suitable material, for instance of thin hard wood. The effect of this mounting is that the sounding board 14 shares the vibrations of the loud speaker and improves its tone. The tone may be modified at will by suitable design of the thickness and other dimensions of the sounding board.

Improved means are provided for varying in simple fashion the distance of the electromagnet from its armature. These are shown in Figures 1 and 2. The electromagnet system as a whole is fastened on a plate 16 to which is attached a stem 7. This stem can slide in a long sleeve 18 which extends from Y the casing 15. The stem is threaded at its end at 20 to receive a nut 21 which bears upon theend 22 of the sleeve 18. A spring 23 presses the electromagnet 2 towards its armature 1,

and by turning the nut 21 the electromagnet may be allowed to approach the armature or may be withdrawn from it. The movement is always precisely axial by reason of the length of the stem 17 and sleeve 18.

It will be understood that this means of guiding, and the means of mounting ina sounding board, although particularly applicable to loud speakers, may also be applied with advantage to any similar instrument, and suchapplications are to be considered within the scope of the invention.

That I claim is 1. An asynchronous vibrating armature for loud speakers comprising, in combination, a rectilinear magnetic body, a pair of parallel arms on said body of different widths and a third arm on said body portion inalignment with said first mentioned arms, said third arm having a thickness less than said first mentioned arms. 1

2. An asynchronous vibrating armature for loud speakers comprising, in combination, a rectilinear magnetic body, a pair of integral arms on said body of different widths and a third arm integral with said body in alignment with said first mentioned arms, said third arm having a thickness less than said first mentioned arms.

3. An asynchronous vibrating armature for loud speakers comprising, in combination, a rectilinear magnetic body, a pair of arms of equal widths and different thickness extending from said body, said arms being disposed in alignment, a longitudinally nonsymmetrically disposed slot formed in the thicker of said arms and holes formed in said arms adjacent their extremities for receiving fastenmg screws.

4. An asynchronous vibrating armature for loud speakers comprising, in combination, a rectilinear magnetic body, a pair of arms of equal widths and different thickness extending from said body, said arms being disposed in alignment and a longitudinally nonsymmetrically disposed slot formed in the thicker of said arms.

5. An asynchronous vibrating armature for loud speakers comprising in combination, a rectilinear magnetic body, a pair of arms of equal widths and different thickness integral with said body, said arms being disposed in alignment, a longitudinally nonsymmetrical- 1y disposed slot formed in the thicker of said arms and holes formed in said arms adjacent their extremities for receiving fastening screws.

6. An asynchronous vibrating armature for loud speakers comprising, in combination, a rectilinear magnetic body, a pair of arms of equal widths and different thickness integral w1th said body, said arms being disposed in alignment and a longitudinally nonsymmetrically disposed slot formed in the thicker of said arms.

7. Anasynchronous'vibrating armature for loud speakers comprising, in combination, a rectilinear magnetic body, a pair of parallel arms on said body of different widths, a third arm on said body ortion in alignment with said first mentioned arms, said third arm having a thickness less than said first mentioned arms and means adapted to transmit the vibrations of said body to the vibrating membrane of the said loud speaker, disposed centrally on said body.

8. An asynchronous vibrating armature for loud speakers comprising, in combination, a rectilinear magnetic body, a pair of integral arms on said body of difierent widths, a third arm integral with said body in alignment with said first mentioned arms, said third arm having a thickness less than said first mentioned arms and means adapted to transmit the vibrations of said body to the vibrating membrane of said loud speaker, disposed centrally on said body.

9. An asynchronous vibrating armature for loud speakers comprising, in combination, a

rectilinear magnetic body, a pair of arms of equal widths and different thickness extending from said body, said arms being disposed in alignment, a longitudinally nons mmetrically disposed slot formed in the t icker of said arms and means adapted to transmit the vibrations of said body to the vibrating mem brane of said loud speaker, disposed centrally on said body.

1 10. An asynchronous vibrating armature for loud speakers comprising, incombination,

a rectilinear magnetic body, a pair of arms of equal widths and difierent thickness extending from said body, said arms being disposed in alignment, a longitudinally nons mmetricall disposed slot formed in the t icker of sai arms, holes formed in said arms adjacent their extremities for receiving fastenin screws and means adaptedto transmit the v1 brations of said body to the vibrating membrane of said loud speaker, disposed centrally on said body.

11. An asynchronous vibrating armature for loud speakers com rising in combination, a rectilinear magnetic dy, a pair of arms of equal widths and different thickness inte ,al with said body, said arms being dispose in ali nment, a'longitudinally nonsymmetrically is ed slot formed in the thicker of said arms, oles formed in said arms adjacent their extremities for receiving fastening screws and means adapted to transmit the vibrations of said body to the vibrating membrane of said loud speaker, disposed centrally on said-body. 12. An asynchronous vibrating armature for loud speakers comprising, in combination, arectilinear magnetic body, a pair of arms of equal widths and different thickness inte al with said body, said arms being dispose in ali ment, a lon itudinally nonsymmetrical ly isposed slot formed in the thicker of said arms and means adapted to transmit thevibrations ofsaid body to the vibrating membrane of said loud speaker, disposed centrally on said body. r

In testimony whereof I have signed my name to this specification.

FELIPE SALDANA. 

